Paint stripping system



Nov. 5, 1963 M. EVANS ETAL PAINT STRIPPING SYSTEM 2 Sheets-Sheet 1 Filed Sept- 5, 1959 United States Patent 3,109,439 lAlNT STRIPPING SYTEM Dewey M. Evans, Plymouth, Orlan M. Arnold, Grosse Pointe Park, and Francis G. Rylance, Farmington, Ilia ling assignors to Ajem Laboratories, Inc., Livonia,

Filed Sept. 3, 1959, Ser. No. 837,872 8 Claims. (Cl. 13474) This invention relates to a paint stripping system and, more particularly, to a continuously operating system for stripping or removing from moving objects paint sprayed or otherwise accumulated thereon.

In the continuous production line manufacture of varione machine parts, such as, for example, in the automobile industry, parts which are to be painted or coated are moved in production line fashion more or less continuously past a paint spraying or applying station where the paint or other coating is applied. It may be, however, that some of the parts so painted are defective in some respect or the coating of paint improperly applied so that the defective parts are rejected at a subsequent inspection station and returned for re-pain-ting or adjustment. After such adjustment or correction of the defection and/or prior to repainting the part it may be desired to strip therefrom the first applied coating.

Also, if such parts are carried continuously through the painting station on production line conveyors such as, for example, overhead monorail conveyors or other types of continuously moving supporting conveyors, the hooks or carriers or supporting members on the conveyor may accumulate a considerable amount of paint as they carry the parts being painted through the painting station. Since the conveyor members repeatedly pass through the paint station, paint may accumulate on the conveyor members to a depth which interferes with the adequate hanging or supporting thereon, and the accumulation of paint on the conveyor support may contaminate the part being conveyed in the vicinity of contact therebetween with, accordingly, some discoloration or imperfections produced on the part being painted, particularly when the part is being painted a different color than was applied to the part which that particular conveyor last conveyed through the painting station.

If it is attempted to remove accumulations of paint from such conveying supporting members periodically, some shutdown of the conveyor operation is required as Well as substantial man hours to accomplish the task. If on the other hand, it is attempted to remove such accumulations chemically, it may be found that the requisite stripping baths are expensive and/ or merely loosen or soften the accumulated paint requiring a substantial manual removal and/ or again require keeping the conveyor out of operation while the conveyor members are soaked in or subjected to treament by the chemical stripping material.

Also, in the treating of various parts other than painted parts, it may be desired to wash and/or remove therefrom residual material and/or previously applied compositions used in the stamping, extruding, drawing, bufling, or other operations to clean the parts quickly and thoroughly and automatically prior to assembly thereof in the ultimate device.

According to this invention, however, a system is provided for automatically stripping or cleaning paint or other materials from conveyor supports or parts carried by a continuously moving conveyor line or otherwise at the speed at which the conveyor moves, and as a continuous part of the conveyor or other operation so that the conveyor and/ or parts carried thereby are maintained clean and stripped of paint and other soil. Furthermore, according to this invention, methods and apparatus are provided for accomplishing this in substantially closed 3,109,439 Patented Nov. 5, 1963 tanks to minimize any possible fire hazard and/ or evaporation loss, and by combining dipping, scrubbing, spraying and rinsing steps and techniques, the conveyor and/ or part-s carried thereby are completely stripped of paint and dried within a relatively compact space and yet without stopping the conveyor or slowing it down below the normal conveying operating speed thereof.

One object of this invent-ion is to provide a system of the character described for continuously stripping from a continuously operating conveyor and/ or parts carried thereby paint sprayed thereon, and for scrubbing and rinsing and drying the conveyor and parts at normal operating conveyor speed.

Another object of this invention is to provide apparatus of the character described for stripping paint from a continuously operating conveyor, which apparatus is substantially entirely enclosed against evaporation losses and fire hazards and includes means for continuously removing from such apparatus paint stripped from a conveyor passing therethrough.

A further object of this invention is to provide apparatus of the type described for a continuously moving conveyor including means for submerging the conveyor in a forcefully agitated stripping liquid to scrub and loosen accumulations of paint on the conveyor and means for removing the loosened paint, rinsing the conveyor, and drying it without impeding the speed or continuous operation of the conveyor.

Still another object of this invention is to provide a system of the character described for continuously cleaning paint or other soil from continuously moving machine parts as they are moved through a tank of cleaning liquid and for providing submerged jets for directing a scrubbing jet turbulence in said liquid in said tank against parts being conveyed therethrough.

Still another object of this invention is to provide a method of the character described for removing accumulations of paint from a continuously moving conveyor without impeding the speed or continuous operation thereof and including the steps of immersing the conveyor in a stripping liquid, producing a forceful agitation scrubbing action on the immersed conveyor in the stripping liquid, spraying and scrubbing the conveyor after exiting from the stripping liquid to remove softened portions of paint still clinging to the conveyor, and rinsing and drying the conveyor for reuse.

A still further object of this invention is to provide apparatus of the character described including a substantially continuous enclosed treating tunnel or trough in which the conveyor is immersed in a stripping liquid, which tunnel or trough includes baffle members for controlling agitation therein to scrub paint from the conveyor and collect the scrubbed paint at a predetermined level in the tunnel or trough, as well as skimming or other removal means for continuously removing from stripping liquid in the apparatu accumulations of paint scrubbed or stripped from the conveyor.

Other objects and advantages of this invention will be apparent from the following description, the attached drawings and the appended claims.

In the drawing FIG. 1 is a side view, with parts broken away, of appanatus embodying this invention;

FIG. 2 is a top view of the apparatus of FIG. 1;

FIG. 3 is a vertical section along the line 3-3 of FIG. 1;

FIG. 4 is a vertical section along the line 44 of FIG. 1; and

FIG. 5 is a vertical section along the line 5-5 of FIG. 1.

Referring to the drawings in which like reference numbers denote like parts throughout the several views thereof, apparatus embodying this invention is illustrated for the stripping of paint from the pulleys and hooks of an overhead monorail conveyor the carrying rail of which is indicated at with a depending moving hook arrangement 11 depending therefrom and adapted in known manner, to move continuously along rail 10 through a production line for carrying machine parts utilized in the production line. The stripping apparatus itselfv includes a number of sections which can be generally designated as an immersion tank section 12, a spray stripping section 13, a rinsing section 14, and a drying section 15.

The embodiment of apparatus is illustrated here as applied to an overhead monorail conveyor. Accordingly, the conveyor enters the apparatus at the left side of FIG. 1 at the normal overhead operating height of rail 10 through an entrance hood section 16. For convenience in installation and maintenance, however, the apparatus rests on the floor and, accordingly, rail 10' of the conveyor dips as indicated in the drawing to the level of the immersion section 12. This immersion section 12 is essentially a closed tank of substantial longitudinal extent and containing the stripping liquid for softening and attacking paint which may have accumulated on conveyor hooks 11 and/or parts carried thereby. Conveyor rail 10 runs along the inside of the top of tank 12 as indicated in the drawings, and the level of liquid is maintained so as substantially to fill the immersion tank 12 and completely immerse conveyor hooks 11 as they pass through the immersion section from left to right in the drawings moving at the regular operating speed of the conveyor.

An offset tank 2t) is provided adjacent the terminal end of immersion sectioni12 and in direct communication therewith. Mounted above this offset tank is a centrifugal pump 21 driven by a motor 22 through a suitable drive indicated at 23. Preferably, centrifugal pump 21 is of the known variety that has a centrally located intake and a peripheral discharge, and pump 21 is mounted at a height such that the intake thereof is but slightly below the level of liquid in tank 20 so as to skim from the top of the liquid in tank 20 softened paint and other materials removed in the apparatus from hooks 11 passing therethrough.

Thus centrifugal pump 21 is provided as a skimming pump, for either continuous or intermittent operation as desired, to remove from the stripping liquid in the apparatus any paint or other material stripped therein from the monorail hooks 11. At any convenient point along immersion section 20 a sludge separator 25 is provided of known construction to withdraw continuously or intemittently immersion section 12 any paint or other materials stripped from the monorail hooks 11 which settles out from the liquid in the immersion section, instead of floating to the surface for removal thereof by skimming pump 21, it beingunderstood that whether paint stripped from hooks 11 floats or settles out depends upon the composition thereof.

Also mounted above offset tank 20 is a centrifugal recirculating pump 30, driven by motor 31 through a suitable drive indicated at 32. Recirculating pump takes the stripping liquid from offset tank 20 and, at substantial pressure, pumps it through a manifold 35 extending along and around the lower portion of immersion section 12 from which manifold the stripping liquid is discharged at substantial pressure and velocity through a plurality of nozzles 36, a substantial portion of which are inclined to direct the jet streams therefrom toward the left in the drawing and against the direction of travel of hooks 11 for providing forceful agitation. and physical scrubbing action of the stripping liquid in immersion section-12 against advanced hooks '11. Others of the nozzles 36 are preferably directed transversely and/ or at different levels of immersion section 12 to enhance the agitation and scrubbing action and dispersion of paint stripped from hooks 11 to urge it either to float on the surface for skimming by pump 21 or to settle to the bottom for removal by sludge remover 25 or such other sludge remover or conveyor as may be provided.

Since many of the painting compositions and materials in the stripping liquid are quite volatile and obnoxious in various manners to varying degrees, exhaust blower devices indicated generally at 49 and 41, and driven respectively by motors 42 and 4 3, are provided at various points along immersion section 12, and particularly at the entrance a-nd exit ends thereof, to withdraw therefrom and exhaust safely from the building obnoxious or dangerous fumes which may result from the stripping action, the paint being stripped, or the stripping liquid. Such units at each end of the stripping trough also may provide an air curtain against escape of fumes into the room.

Furthermore, and particularly with volatile stripping liquid, a water seal is preferably provided in cases where the stripping liquid, although volatile, is heavier than and not readily miscible with water. That is, particularly as indicated in FIG. 3, a relatively thin layer 45 of water is maintained floating on the top surface of the stripping liquid to curtail the evaporation thereof. In such a case, objectionable disturbance of the interface between such water sealing layer and the stripping liquid is satisfactorily minimized by the provision of transverse baffles 50 adjacent such interface and extending along substantially the entire length of immersion section 12 and across substantially the entire width thereof on either side of monorail 10. Thus hooks 1 1 may be carried through the stripping liquid and scrubbed with forceful agitation therein, but the effects of this movement and agitation on the water sealing layer 45 are interrupted and/or minimized by baffles 50. As noted above, some of the jet nozzles 36 from manifold 35 are directed to different levels in immersion section 12, and such of the nozzles 36 as may be directed upwardly provide for urging floating paint or other material removed from hooks :11 along the baffle 50 to the skimming pump to prevent undesirable accumulation of floating debris under baffles 50.

As will be understood, the particular length of immersion section 12 is correlated with the speed of conveyor hooks 11 as well as the strength or harshness of the stripping liquid to provide adequate contact or immersion time for softening and/or removal of the accumulation paint from hooks 11 by the immersion and scrubbing action in immersion section 12. At the exit end of immersion section 12, the monorail 10 rises to withdraw hooks 11 from the immersion in the stripping liquid and to guide them through spray stripping section 13 where a concentration of jet spray nozzles in manifold 35 deliver a violent spray against the hooks 11 as they emerge from the immersion section 12 for further mechanical scrubbing action to remove or strip therefrom accumulations of paint which may have been softened but not completely removed during immersion in section 12. As will be noted from the drawing, material removed from hooks 11 in spray stripping section 13 will be returned along with the sprayed liquid back into the body of liquid in immersion section 12 to be removed therefrom either by skimming pump 21 or sludge separator 25.

From spray stripping section 13, hooks 11 are carried on monorail 10 into a rinsing section 14 where the hooks are sprayed, preferably by a rinsing liquid, to rinse therefrom any remaining paint not heretofore removed as well as the stripping liquid which may still be clinging thereto. As shown in the drawings rinsing section 14 includes an upper enclosed hood or covered tunnel part6t3 the walls and top of which are preferably continuations with spray stripping section 13. Below tunnel is a rinse liquid tank 61 from which rinse liquid is continuously withdrawn by pump 62, driven by motor 63 through a suitable drive 64, and pumped through manifold 65 from which it is ejected through jet spray nozzle 66 to impinge upon hooks 11 as they are carried through rinse section 14 on rail 10.

After being rinsed in rinse section 14, hooks 11 proceed on rail 14) to draining and drying section 15 including a closed tunnel portion 70 forming an enclosed continuation of tunnel 60. Here the hooks are subjected to the drying action of a stream of drying air, preferably heated, and supplied to drying section 15 by a conventional blower arrangement indicated at 71 as being driven by motor 72 through a suitable drive 73. From drying section 15 hooks 11 proceed on monorail 10 in cleaned and dried condition and ready to enter again the first station on the production line, to receive additional parts to be conveyed to a painting station, etc.

Satisfactory results have been obtained with this invention in the removal of paints such as are conventionally applied to automobile wheel discs, body parts, etc.e.g., nitro-cellulose base lacquers, linseed oil or tung oil base paints, etc.by utilizing a system according to this invention in which the stripping liquid in immersion section 12 comprises trichloroethylene, perchloroethylene, or 1,1,l-trichloroethane and like solvents. Actually, with some paint materials, satisfactory results are obtained with a stripping liquid comprising a strong (e.g., about 10%) aqueous caustic solution as is used in conventional paint stripping operations, although the organic materials are preferred for most installations (with, of course, a covering layer of water 45) and particularly where the utilization of a more efficient organic stripping liquid permits a shorter immersion time and, consequently, a shorter immersion section 12 in the apparatus. In some cases with types of paint or coating which are particularly difficult to remove (such as some Gilsonite chassis paint, and the like) a detergent-solvent stripping liquid is used of the type, for example, as is disclosed in the copending application of Arnold et al., S.N. 479,032, filed December 31, 1954, now Patent No. 2,982,723, and assigned to the same assignee as the present application.

Satisfactory results are obtained by using as a rinsing liquid in tank 61 for spray application in rinse section 14 clear water although, with some materials which are particularly difficult to remove, a conventional aqueous detergent rinsing solution may be preferred.

It will accordingly be seen that, in a system embodying this invention, methods and apparatus are provided for the continuous stripping for accumulations of paint or ther materials from parts on a moving conveyor without impeding the continued operation or speed of the conveyor, and that provision is made for utilizing even highly volatile stripping and rinsing liquids with minimum evaporation losses and with avoidance of hazardous or obnoxious escape of the volatile materials into the area adiacent the stripping operation. Notwithstanding the provisions of means for forceful agitation and mechanical scrubbing action against the conveyor parts, a water layer seal may be provided over the surface of the stripping liquid, and materials stripped from the conveyor parts are continuously or intermittently removed from both the surface portion and lower portions of the stripping liquid.

As noted above, the foregoing considerations are also to be considered applicable to the cleaning of various machine parts, in addition to paint stripping, to remove therefrom various soils and residual compositions which may have been applied to or otherwise accumulated on the parts during stamping, extruding, drawing, bufiing, machining, etc., operations and, for example, prior to assembling these parts in the ultimate device or assembly for which they are intended. Utilizing a system in accordance with the foregoing, particularly including a closed tank through which the parts are moved submerged in a cleaning liquid, enhanced results are achieved from the standpoint of length of cleaning time and required space occupied by the cleaning apparatus. Also, as noted above, it is preferred to have at least some of the submerged jets 36 directed against the line of movement of the parts through the tank, and, preferably, positioned as close as possible to the parts being cleaned and to direct a jet of cleaning liquid tangentially to the surface of the part. Utilizing such arrangements, high liquid pressure can be provided in manifold 35 for forceful impingement through jets 36 on the parts being stripped or cleaned and substantially without disturbing or requiring intense agitation of the bulk of the cleaning liquid in tank 12.

While the methods and forms of apparatus herein described constitute a preferred embodiment of the invention, it is to be understood that the invention is not limited to these precise methods and apparatus, and that changes may be made therein without departing from the scope of the invention as defined in the accompanying claims.

What is claimed is:

1. In apparatus of the character described for cleaning traveling hooks of a monorail conveyor by submerging said hooks in a volatile cleaning liquid while said conveyor is in continuous operation, the combination which comprises a closed elongated stripping tank for containing a supply of said volatile cleaning liquid, means for moving said hooks submerged in said liquid through said tank during said continued operation of said conveyor, means for supplying to the surface of said volatile cleaning liquid a floating layer of a sealing liquid less volatile and lighter than said volatile cleaning liquid for inhibiting evaporation of said cleaning liquid, a manifold having nozzles in the lower part of said tank spaced a substantial distance below said layer of sealing liquid, pump means for recirculating cleaning liquid through said manifold and out of said nozzles for creating jet turbulence in said tank for scrubbing action against said books, a substantial number of said nozzles being directed against the direction of travel of said books through said tank, and transverse baffle means in said tank extending substantially throughout the length and width thereof and positioned adjacent the interface between said cleaning liquid and said sealing liquid for inhibiting at said interface agitation effects created by said jet turbulence and said movement of said hooks.

2. In apparatus of the character described for cleaning and stripping paint and other soil from machine parts by submerging in a volatile cleaning liquid while said parts are continuously conveyed with a continuously moving conveyor, the combination which comprises a substantially closed stripping tank for containing a supply of paint and soil stripping liquid, means for submerging said machine parts into said stripping liquid in said tank while being conveyed by said conveyor through said tank, pumping and nozzle means for continuously recirculating said stripping liquid through said tank and including means for directing against said parts submerged jets of said liquid for scrubbing action in said tank below the surface of said stripping liquid therein, said submerged jets being directed against the direction of movement of said machine parts through said tank for scrubbing action against said parts, means for raising and removing said parts from said stripping liquid after a predetermined contact and for collecting and returning to said tank paint and soil dripping from said parts, a rinse chamber separate from said tank, means including said conveyor for conducting said parts through said rinse chamber, and means for spraying a rinse liquid onto said parts for rinsing therefrom residual stripping liquid and paint or soil softened or stripped thereby.

3. In apparatus of the character described for cleaning machine parts by submerging them in a volatile cleaning liquid, the combination which comprises an elongated cleaning and stripping tank for containing a supply of said volatile cleaning liquid, means for moving said parts substantially continuously through said tank and submerged in said liquid, means for supplying to the upper surface of said cleaning liquid a floating layer of a sealing liquid less volatile and lighter than said cleaning liquid for inhibiting evaporation of said cleaning liquid from said tank, a manifold having nozzles in the lower part of said tank and beneath said surface of said cleaning liquid, pump means for recirculating said cleaning liquid through said manifold and out of said nozzles for creating jet turbulence in said tanks, said nozzles being positioned to direct said jet turbulence against the direction of said movement of said parts through said tank for scrubbing action of said liquid against said parts.

4. In apparatus of the character described for cleaning machine parts by submerging them in a volatile cleaning liquid, the combination which comprises an elongated cleaning and stripping tank for containing a supply of said volatile cleaning liquid, means for moving said parts substantially continuously through said tank and submerged in said liquid, means for supplying to the upper surface of said cleaning liquid a floating layer of a sealing liquid less volatile and lighter than said cleaning liquid for inhibiting evaporation of said cleaning liqud from said tank, a manifold having nozzles in the lower part of said tank and beneath said surface of said cleaning liquid, pump means for recirculating said cleaning liquid through said manifold and out of said nozzles for creating jet turbulence in said tanks, said nozzles being positioned to direct said jet turbulence against the direction of said movement of said parts through said tank for scrubbing action of said liquid against said parts, and transverse bafile means in said tank extending substantially throughout the length and Width thereof and positioned adjacent the interface between said cleaning liquid and said sealing liquid for inhibiting at said interface agitation effects created by said jet turbulence and said movement of said parts.

5. In apparatus of the character described for cleaning and stripping paint and like soil from traveling hooks of a monorail conveyor by submerging said hooks in a cleaning liquid while said conveyor is in continuous operation, the combination which comprises an elongated cleaning and stripping tank for containing a supply of said cleaning liquid, means for submerging said hooks into said supply of liquid in said tank and for conveying said hooks therethrough during said continued operation of said conveyor, a manifold having a plurality of nozzles within said tank and submerged in said liquid therein, pump means for continuously recirculating said a liquid in said tank and for ejecting from said nozzles jets of said liquid impinging upon said hooks passing through said tank for direct scrubbing action against said hooks for softening and stripping said paint and soil therefrom, and means for continuously skimming from the surface of said liquid in said tank floating soils re moved from said hooks and for removing adjacent the bottom of said tank non-floating soils removed from said hooks. V

6. Apparatus as recited in claim'5 which also includes a rinsing chamber separate from said tank and through which said conveyor hooks are continuously moved, and means for spraying a rinsing liquid onto said hooks for rinsing therefrom said paint and soils softened and scrubbed in said tank.

7. Apparatus as recited in claim 6 which also includes a drying chamber sequentially positioned beyond said rinsing chamber and through which said hooks are continuously conveyed by said conveyor.

8. Apparatus as recited in claim 5 in which said submerged nozzles are distributed along said tank for directing said scrubbing jets of liquid to impinge upon said hooks against the direction of travel thereof through said tank.

References Qited in the file of this patent UNITED STATES PATENTS 1,390,268 Beckett Sept. 13, 1921 1,624,982 Rosenberg Apr. 19, 1927 1,964,275 Secondo June 26, 1934 2,013,522 Mills Sept. 3, 1935 2,101,840 Dinley Dec. 14, 1937 2,114,782 Kohler Apr. 19, 1938 2,180,947 Ball Nov. 21, 1939 2,207,697 Kendall July 16, 1940 2,219,007 Dostal Oct. 22, 1940 2,270,642 Somes Jan. 20, 1942 2,273,939 Dammers Feb. 24, 1942 2,635,064 Faler Apr. 14, 1953 2,635,614 Ford Apr. 21, 1953 2,689,198 Judd Sept. 14, 1954 2,710,819 Weber June 14, 1955 2,838,289 Northrup June 10, 1958 

3. IN APPARATUS OF THE CHARACTER DESCRIBED FOR CLEANING MACHINE PARTS BY SUBMERGING THEM IN A VOLATILE CLEANING LIQUID, THE COMBINATION WHICH COMPRISES AN ELONGATED CLEANING AND STRIPPING TANK FOR CONTAINING A SUPPLY OF SAID VOLATILE CLEANING LIQUID, MEANS FOR MOVING SAID PARTS SUBSTANTIALLY CONTINOUSLY THROUGH SAID TANK AND SUBMERGED IN SAID LIQUID, MEANS FOR SUPPLYING TO THE UPPER SURFACE OF SAID CLEANING LIQUID A FLOATING LAYER OF A SEALING LIQUID LESS VOLATILE AND LIGHTER THAN SAID CLEANING LIQUID FOR INHIBITING EVAPORATION OF SAID CLEANING LIQUID FROM SAID TANK, A MANIFOLD HAVING NOZZLES IN THE LOWER PART OF SAID TANK AND BENEATH SAID SURFACE OF SAID CLEANING LIQUID PUMP MEANS FOR RECIRCULATING SAID CLEANING LIQUID THROUGH SAID MANIFOLD AND OUT OF SAID NOZZLES FOR CREATING JET TURBULENCE IN SAID TANKS, SAID NOZZLES BEING POSITIONED TO DIRECT SAID JET TURBULANCE AGAINST THE DIRECTION OF SAID MOVEMENT OF SAID PARTS THROUGH SAID TANK FOR SCRUBBING ACTION OF SAID LIQUID AGAINST SAID PARTS. 